Known load changeover switches for tap changers of regulating transformers usually have a so-called resistance fast changeover switching, the switching contact shafts of which are controlled by a cam disk transmission that in turn is driven by an energy store. In that regard, the cam disk moves in an oscillating motion between two end positions and, in particular, in dependence on the respective direction of movement of the selector. This means that the contacts that have closed first in the case of a first rotational direction of the cam disk open first when a return movement takes place. The contacts that have opened first in the same rotational direction of the cam disk close last when the return movement takes place.
DE 100 50 821 C1 discloses a mechanical switch contact for double-pole interruption for a tap changer. The switch contact comprises an insulating material carrier on which are arranged fixed contacts that are constructed as spherically shaped contact regions. In addition, rotatably mounted on the insulating material carrier is a contact carrier that is connected with a pivot arm pivotable through a defined angle. A contact member is fastened to the free end of the pivot arm and has in turn contact rollers at its two ends. The fixed contacts are selectably electrically connectable by these contact rollers. Depending on the respective position of the pivot arm the contact rollers impinge on the spherical surface of respective oppositely arranged fixed contacts and in this manner produce respective electrical contact connections.
A further mechanical switch contact for switching over in an on-load tap changer is known from WO 2007/042088 A1. This mechanical switch contact also has an insulating material carrier at which fixed contacts, with which electrical connection can be made, are arranged. In addition, rotatably mounted on the insulating material carrier is a switch lever that has a pivot arm at one of its two free ends and an actuating profile at the other free end. The switch lever is, in the case of action of force on the actuating profile, abruptly pivotable from one of its two stationary states into the respective other stationary state. A contact housing pivotable about a separate bearing is additionally mounted on the insulating material carrier and carries two parallel, electrically interconnected contact fingers that respectively surround at both sides the electrically connected fixed contacts. The contact housing is disposed in mechanical connection with the switch lever and is actuatable by this. The switch lever can in addition comprise an entrainer that mechanically positively engages in an entrainer opening of the contact housing. One of the two fixed contacts can be selectably constructed as a contact rail, on which the contact fingers slide during movements of the contact housing.
It is common to the actuating mechanisms for known mechanical switch contacts for switching over in on-load tap changers that the switching over takes place between two end positions so that oscillating switching movements are required.
WO 898/08924 A discloses a spring jump drive for load changeover switches of tap changers, the storage spring of which can be stressed by a drive, the shaft of which rotates either in or counter to clockwise sense, wherein an element, which is driven by the storage spring during the switching-over process, for the contact movement executes a rotational movement. The element for contact movement can be, for example, a cam disk or a gate control. The storage spring and the driven element are connected with a coupling element that is rotatable only in one direction regardless of the rotational direction of the drive. This known spring jump drive serves for contact sequence control and is particularly suitable for thyristor load changeover switches.